Most trendy diets claim that all carbohydrates are bad guys, yet of the three macronutrients that provide calories in our diet (carbs, protein, and fat), carbohydrates are the body’s primary fuel source. They’re responsible for managing your heart rate, digestion, breathing, exercising, walking, and thinking.

Roughly 70 percent of your daily calories should come from good (complex) carbohydrates. The ones to avoid are called simple carbs.

Both types of carbs are sugars. Both are digested and converted into glucose, which is used by the body for energy: in the blood as glucose, or stored in either the muscles or the liver as glycogen. When consumed in excess, carbohydrates can be converted to fat.

Simple carbohydrates include table sugar, molasses, honey, alcohol, white bread, white pasta, white rice, fried chips, sugary cereals, fruit juices, candy, and milk. Most simple carbs are nutritionally empty because they have been tinkered with by humans, stripped of their fiber, minerals, and vitamins. They are digested quickly by the body and cause a sharp spike in your blood sugar levels.

In response to this spike, your pancreas pumps out insulin to transport and deliver the energy-bearing glucose to cells throughout your body. This process causes your blood sugar and insulin levels to swing like a pendulum, leaving you feeling fatigued, hungry, and craving still more simple carbohydrates.
And because simple carbohydrates are digested so quickly, any excess sugar is converted to fat. For these reasons, most simple carbohydrates are a poor food choice.

In contrast, complex carbohydrates are nutritious, and include vegetables, whole grain breads and pastas, beans, peas, brown rice, sweet potatoes, oats, fruits, and whole grain cereals. They are loaded with fiber, vitamins, minerals, and micronutrients. Unlike simple carbohydrates, complex carbohydrates cause a balanced and controlled release of sugar into your system. This slow release gives the body more time to use the carbohydrates as fuel; as a result, fewer turn to fat and insulin remains stable.
So if you consume, whole, good, natural carbs, you will enjoy more consistent energy throughout the day without gaining extra pounds.

As you can see, the two types of carbs differ immensely from a nutritional standpoint. Simple carbohydrates are calorie laden, providing little nutrition and causing weight gain. Complex carbohydrates are lower in calories and, because they are loaded with fiber, provide bulk that fills you up sooner, alleviates hunger pangs, and keeps you feeling satisfied longer.